The activities of the Tissue Bioprinting program include: i) Develop bioprinting protocols to fabricate native-like, functional human tissues. Ii) Validate of printed tissues: develop morphological and physiological biomarkers of tissue architecture and function by using microscopy, histology, gene sequencing, electrophysiological and other methodologies. iii) Use printed tissues for the screening of focused libraries of compounds for drug discovery. iv) Develop a framework for the sharing of validated protocols as a readily available resource for researchers to exchange data on optimized conditions for bioinks, culture techniques, cell types, and software tools as well as techniques to quantify and validate printed tissues. Bioprinting of tissue models for pain, opioid addiction and relapse: As part of the Trans-NIH Opioid Initiative, the 3D Tissue bioprinting group will establish tissue models for testing compounds for the treatment of pain and addiction. Currently, a prototype of a human blood brain barrier (BBB) tissue model containing microvasculature, pericytes, and astrocytes in a multiwell format is been developed based on published protocols. As interactions with the BBB are keys to understanding opioid transport, we will introduce opioid into the microvessels of the brain model and study opioid transport across the BBB. A 3D brain model that includes dopaminergic, GABAergic and glutaminergic neurons derived from human iPSCs will be developed as models for addiction. In addition to the human brain model, the 3D biofabrication platform will also enable the development of tissues containing sensory neurons and cells involved in the inflammatory response which will allow the development of tissue models for testing the effect of compounds in pain sensation and resolution. In addition to the NCATS intramural efforts, participating ICs may choose to issue supplements to existing extramural grants to advance the creation of 3D bioprinted tissue models.